I'm trying to perform a cell optimisation on a crystal of YBCO however the calculations always seem to spit out nonsense (the cell volume continually increases). I am using the structural data found on the open crystallography database which should be accurate. Is there perhaps something wrong with the unit cell I've chosen? The input is provided below:<div><br /></div>
<p>&FORCE_EVAL</p>
<p> METHOD Quickstep</p>
<p> &DFT</p>
<p> BASIS_SET_FILE_NAME BASIS_MOLOPT</p>
<p> POTENTIAL_FILE_NAME GTH_POTENTIALS </p>
<p> LSD</p>
<p> &POISSON</p>
<p> POISSON_SOLVER PERIODIC </p>
<p> PERIODIC XYZ</p>
<p> &END POISSON</p>
<p> </p>
<p> &MGRID</p>
<p> NGRIDS 5</p>
<p> CUTOFF 800</p>
<p> REL_CUTOFF 60</p>
<p> </p>
<p> &END MGRID</p>
<p> &QS</p>
<p> METHOD GPW</p>
<p> EPS_PGF_ORB 1E-16</p>
<p> </p>
<p> &END QS</p>
<p> &SCF</p>
<p> &SMEAR ON</p>
<p> ELECTRONIC_TEMPERATURE 1000</p>
<p> METHOD FERMI_DIRAC</p>
<p> &END SMEAR</p>
<p> ADDED_MOS 700</p>
<p> CHOLESKY INVERSE</p>
<p> SCF_GUESS RESTART</p>
<p> EPS_SCF 1.0E-6</p>
<p> MAX_SCF 250</p>
<p> </p>
<p> </p>
<p> </p>
<p> &DIAGONALIZATION ON</p>
<p> ALGORITHM STANDARD</p>
<p> &END DIAGONALIZATION</p>
<p> &MIXING T</p>
<p> METHOD BROYDEN_MIXING</p>
<p> ALPHA 0.5</p>
<p> BETA 1.5</p>
<p> NBUFFER 15</p>
<p> </p>
<p> &END MIXING</p>
<p> </p>
<p> &END SCF</p>
<p><br /></p>
<p>&KPOINTS </p>
<p> SCHEME MONKHORST-PACK 2 2 2</p>
<p> FULL_GRID yes</p>
<p> SYMMETRY yes </p>
<p> VERBOSE yes </p>
<p> PARALLEL_GROUP_SIZE -1</p>
<p>&END KPOINTS</p>
<p><br /></p>
<p> &XC</p>
<p> &XC_FUNCTIONAL PBE</p>
<p> &END XC_FUNCTIONAL</p>
<p> &XC_GRID</p>
<p> USE_FINER_GRID T</p>
<p> &END XC_GRID</p>
<p> &END XC</p>
<p><br /></p>
<p> &END DFT</p>
<p> &SUBSYS</p>
<p> &COORD</p>
<p><br /></p>
<p>Cu 0 0 0</p>
<p>Y 1.910150 1.942740 5.841745</p>
<p>Ba 1.910150 1.942740 2.148944</p>
<p>Ba 1.910150 1.942740 9.534546</p>
<p>Cu 0.000000 0.000000 11.683490</p>
<p>Cu 0.000000 3.885480 0.000000</p>
<p>Cu 0.000000 3.885480 11.683490</p>
<p>Cu 3.820300 0.000000 0.000000</p>
<p>Cu 3.820300 0.000000 11.683490</p>
<p>Cu 3.820300 3.885480 0.000000</p>
<p>Cu 3.820300 3.885480 11.683490</p>
<p>Cu 0.000000 0.000000 4.147756</p>
<p>Cu 0.000000 3.885480 4.147756</p>
<p>Cu 3.820300 0.000000 4.147756</p>
<p>Cu 3.820300 3.885480 4.147756</p>
<p>Cu 0.000000 0.000000 7.535734</p>
<p>Cu 0.000000 3.885480 7.535734</p>
<p>Cu 3.820300 0.000000 7.535734</p>
<p>Cu 3.820300 3.885480 7.535734</p>
<p>O 0.000000 1.942740 0.000000</p>
<p>O 0.000000 1.942740 11.683490</p>
<p>O 3.820300 1.942740 0.000000</p>
<p>O 3.820300 1.942740 11.683490</p>
<p>O 1.910150 0.000000 4.418579</p>
<p>O 1.910150 3.885480 4.418579</p>
<p>O 1.910150 0.000000 7.264911</p>
<p>O 1.910150 3.885480 7.264911</p>
<p>O 0.000000 1.942740 4.403858</p>
<p>O 3.820300 1.942740 4.403858</p>
<p>O 0.000000 1.942740 7.279632</p>
<p>O 3.820300 1.942740 7.279632</p>
<p>O 0.000000 0.000000 1.850665</p>
<p>O 0.000000 3.885480 1.850665</p>
<p>O 3.820300 0.000000 1.850665</p>
<p>O 3.820300 3.885480 1.850665</p>
<p>O 0.000000 0.000000 9.832825</p>
<p>O 0.000000 3.885480 9.832825</p>
<p>O 3.820300 0.000000 9.832825</p>
<p>O 3.820300 3.885480 9.832825</p>
<p><br /></p>
<p><br /></p>
<p><br /></p>
<p>&END COORD </p>
<p> &TOPOLOGY</p>
<p> </p>
<p> </p>
<p> &END TOPOLOGY</p>
<p> &CELL</p>
<p> SYMMETRY ORTHORHOMBIC</p>
<p> ABC 4 4 12</p>
<p> PERIODIC XYZ</p>
<p> </p>
<p> &END CELL</p>
<p> </p>
<p> </p>
<p> &KIND O</p>
<p> BASIS_SET DZVP-MOLOPT-SR-GTH</p>
<p> POTENTIAL GTH-PBE-q6</p>
<p> &END KIND</p>
<p> </p>
<p> &KIND Ba</p>
<p> BASIS_SET DZVP-MOLOPT-SR-GTH</p>
<p> POTENTIAL GTH-PBE-q10</p>
<p> &END KIND</p>
<p> </p>
<p> &KIND Y</p>
<p> BASIS_SET DZVP-MOLOPT-SR-GTH</p>
<p> POTENTIAL GTH-PBE-q11</p>
<p> &END KIND</p>
<p> </p>
<p> &KIND Cu</p>
<p> BASIS_SET DZVP-MOLOPT-SR-GTH</p>
<p> POTENTIAL GTH-PBE-q11</p>
<p> &END KIND</p>
<p>&PRINT</p>
<p>&CELL HIGH</p>
<p><br /></p>
<p>&END CELL</p>
<p><br /></p>
<p>&END PRINT</p>
<p> </p>
<p> &END SUBSYS</p>
<p> STRESS_TENSOR ANALYTICAL</p>
<p> </p>
<p> </p>
<p>&END FORCE_EVAL</p>
<p>&GLOBAL</p>
<p> PROJECT SZV</p>
<p> RUN_TYPE CELL_OPT</p>
<p> PRINT_LEVEL MEDIUM</p>
<p> </p>
<p> </p>
<p> &END GLOBAL</p>
<p> </p>
<p>&MOTION</p>
<p><br /></p>
<p> &CELL_OPT</p>
<p><br /></p>
<p> KEEP_SYMMETRY .TRUE.</p>
<p> OPTIMIZER BFGS</p>
<p> KEEP_ANGLES</p>
<p><br /></p>
<p> EXTERNAL_PRESSURE [Pa] 100000</p>
<p><br /></p>
<p><br /></p>
<p> &END CELL_OPT</p>
<p><br /></p>
<p><br /></p>
<p><br /></p>
<p><br /></p>
<p><br /></p>
<p><br /></p>
<p><br /></p>
<div>&END MOTION </div><div><br /></div><div><br /></div><div>Many thanks for any help,</div><div>Ash</div>
<p></p>
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